PROJECT SUMMARY This project seeks to use real-time geospatial methods to investigate relationships between social cohesion and social capital within Global Positioning System (GPS)-defined activity space neighborhoods and social networks in relation to HIV pre-exposure prophylaxis (PrEP) uptake and adherence cross-sectionally and longitudinally among transgender women (TW) of color (TWOC) in the New York City metropolitan statistical area (MSA) followed over two years. We will recruit 250 TWOC in the proposed The N2 Study: Transgender Women's Neighborhood and Networks Cohort Study to address the aims of the research. Eligibility requirements include: identifying as a transgender woman (individuals who were assigned a male sex at birth who identify as women, female, trans women, trans female, male-to-female or another diverse trans feminine gender identity on the spectrum) of color; HIV-seronegative; being 18 to 55 years old; residing in the New York City MSA; self-report no plans to move outside of the New York City metropolitan area in the next two years; self-reporting no restrictions to usual physical activity; and self-report willingness to carry a small GPS device for two-weeks at five points over the course of two years. Participants will wear the GPS device following protocols used in our previous feasibility research projects, including studies among TW. In this longitudinal study, six months after completing the initial 2-week GPS protocol, participants will carry the GPS device for an additional 2-weeks every six-months over the two-year study period?for a total of five times. Multiple GPS measures and multiple measures of social networks (at different time points) can better capture the breadth of people's exposure to neighborhood-level factors and dynamics in social networks. Also, GPS activity space environment and social networks data at baseline could potentially influence PrEP outcomes over time, providing a clear temporal ordering and an ability to consider potential time-lags. The proposed study will be the largest GPS study of HIV disparities in any transgender population and presents a remarkable opportunity to study environmental influences on HIV. Findings from the proposed research will impact HIV prevention intervention activities. First, the project will inform specific neighborhood-level policy interventions. For example, increased community efforts through increased social cohesion in neighborhoods may be an HIV prevention intervention that can reduce HIV health disparities. Second, from the GPS dataset we will know the travel patterns of TW and therefore be able to identify optimal geographic locations for HIV prevention interventions. This will advance the literature given that such interventions are seldom geographically targeted. Third, examining changes in spatial mobility (i.e. activity spaces) over time will be useful in knowing whether the risks of particular spaces change or remain constant because different neighborhoods will have different risk profiles. Finally, our dynamic network analysis we propose will deepen understanding of the effects of social networks on HIV prevention behaviors and will improve network-based HIV prevention interventions.